Yuuki's childhood friend and the founder of the Food Research Club. She has an impressive record of being in the same class as Yuuki since grade school. Due to an unknown incident, Chisato hates chocolate. Chisato is shown as a tsundere who harbors feelings for Yuuki since the beginning of the story.

Her brother died when Chisato and Yuuki were kids, which also made her hate chocolate. It is also revealed that she used him as an emotional support for the loss of her brother even to the point of forcing Yuuki to eat chocolate every month instead of her brother.